Converts inositol hexakisphosphate (InsP6) to diphosphoinositol pentakisphosphate (InsP7/PP-InsP5). Converts 1,3,4,5,6-pentakisphosphate (InsP5) to PP-InsP4. . This is the function of ENSG00000176095 (IP6K1, inositol hexakisphosphate kinase 1).